Broach or the like



A ril 9, 1929. o. LUNDELL ,7

BROAGH OR THE LIKE Filed Nov. 29, 1926 Patented Apr. 9, 1929.

UNITED STATES PATENT OFFICE.

OTTO LUNDELL, OF DETROIT, MICHIGAN, ASSIGNOR TO COLONIAL TOOL COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

BROACH OR THE LIKE.

Application filed November 29, 1926. Serial No. 151,338.

It is the primary object of my invention to provide means for lessening the amount of effort necessary to be exerted in pulling a broach, having cutting teeth thereon, through the work being operated upon. It is quite customary in the conventional building of broaches to provide the sides of the cutting teeth with straight faces. These straight faces bear against the sides of the splines or the like which are being cut by the teeth and add greatly to the amount of effort necessary to pull the broach throiwlrtlie work. This is particularly true when the broach has become heated so as to expand to a greater than normal width.

It is therefore an object of my invention to relieve the sides of the teeth, longitudinally of the broach, in proportion to the height of the cutting teeth so as to provide a nearly constant side bearing portion for the teeth and a non-bearing portion on the sides of the teeth which increases as the height of the teeth increases.

Vith the above and other objects in view, my invention consists in the arrangement, combination and construction of the various parts of my improved device, as described in the specification, claimed in my claims, and shown in the accompanying drawings, in which:

Fig. 1 is an elevation of a broach embodying my invention.

Fig. 2 is a sectional view taken on line 22 of Fig. 1.

' illustrated by the two cross sectional views shown in Figs. 2 and 3.

As the depth of the teeth 7 increases toward the finishing end of the broach, a considerable depth is attained and if the sides of the teeth are straight so as to bear in the sides of the splines which are being out, a considerable friction is set up with a consequent increase in the amount of effort required to pull the broach through the Work. As is clearly shown, however, in Fig. 2 the teeth are pro- \'l(l((l with relatively short straight portions 9 and relatively long relieved or inwardly tapered portions 10 which relieved or in wardly tapered portions do not bear against the splines belng out. As is clearly shown by the longitudinal lines in Fig. 1, the depth of the relieved or inwardly tapered portions on the various teeth decreases from the final to the initial cutting end of the broach. The straight or unrelieved portion remains substantialy constant until teeth are of such shallowness as to bring the side portions thereof substantially to a point, as is clearly shown in Fig. 3.

It will be readily appreciated that my invention may be applied tov breaches of different styles and that the number of rows of of teeth provided with cutting end portions,

a portion of the sides of said teeth being straight and a portion thereof tapering inwardly, the straight portions being adjacent the cutting ends of the teeth, and the tapering portions being of increasing depth toward the finishing end of the broach.

2. A broach or the like having a plurality of teeth provided with cutting end portions, a portion of the sides of said teeth being straight and a portion thereof tapering inwardly, the straight portions being adjacent the cutting ends of the teeth and being of substantially the same depth on substantially all of the teeth and the tapering portions being of increasing depth toward the finishing end of the broach.

OTTO LUNDELL. 

